module.exports = async (ctx,next)=>{
    const contentType = 'application/json; charset=utf-8'
    // 设置响应头
    ctx.set('Content-Type',contentType)
    ctx.set('Access-Control-Allow-Origin','*')
    ctx.set('Access-Control-Allow-Methods','OPTIONS,GET,POST,PUT,DELETE')
    await next()
}